1. Field of the Invention
The present invention relates to a laser etching method and a laser etching apparatus for working an article with a laser beam, and more particularly to a laser etching method and a laser etching apparatus capable, in working the article of an inorganic substance, of working without generating deposition around the etching position, and adapted for fine working of a material for a micromachine, an IC or a diode device.
2. Related Background Art
In fine working of a structural member by laser working, it is customary to utilize a harmonic wave of an excimer laser or a YAG laser.
However, as the energy density of the laser light in the oscillated pulse is limited to a level of 100 megawatts at maximum, such laser working method is hardly applicable to an article formed of an inorganic material and is only applicable to the sublimation ablation working of articles principally composed of organic materials. For this reason, the fine working of the article formed of inorganic materials has been achieved by a lithographic process including steps of resist coating, resist patterning by exposure, resist development, etching utilizing the resist pattern and resist ashing for each material, but such process is associated with drawbacks of an increased cost resulting from the complex process steps and a large investment for the production facility in consideration of the process tact time.
In order to resolve such drawbacks, the present applicant proposes, for example in the Japanese Patent Application No. 11-316760, a laser working method for fine working of a structure in an article formed of inorganic materials by sublimation ablation working, utilizing a feature that the laser light emitted from a laser oscillator with a pulse emission time of 1 picosecond or less has a drastically high energy density in time and a feature that the laser light is not converted into thermal energy but is directly converted into a lattice bond cleaving energy because of the very short laser irradiation time.
However the above-mentioned laser working method for sublimation ablation working is capable of etching the article formed of the inorganic material by ablation sublimation, but, in certain materials, the sublimated and gasified atoms or molecules instantly cause recombination, thereby being liquefied and deposited in the etching position in the vicinity thereof-and solidified, whereby the vicinity of the etching position cannot be maintained clean or the etching itself can be prevented by the deposition of such by-products.
Such drawbacks become particularly conspicuous in materials in crystalline or amorphous solid state by covalent bonds. The cause for such phenomenon is not yet clarified, but is considered to be inherent to the materials having covalent bonds of a higher bonding energy, since the above-mentioned drawbacks are not conspicuous in the crystalline materials based on metal bonding or ionic bonding or in the amorphous materials based on ionic bonding.